Tinted mirror



aawmwwv United States Patent U.S. Cl. 117-3 5 Claims ABSTRACT OF THE DISCLOSURE A tinted mirror composed of glass with a tinted surface overcoated with a conventional silver mirror coating, The glass surface is tinted by treating it with a solution containing an organic titanate, a xanthene type dye, a copper salt and a salt of aluminum, lead, antimony or trivalent titanium.

CROSS REFERENCE TO RELATED APPLICATION This application is a division of our copending application for U.S. Letters Patent, Ser. No. 567,388, filed July 25, 1966, now U.S. Patent 3,421,921, issued Jan. 14, 1969.

BACKGROUND OF INVENTION The present invention relates to a colored or tinted mirror and it has particular relation to a coloring solution which can be used to apply a permanent color to a glass mirror.

It has long been a desideratum of the art to be able to dye or color glass articles after the glass has been melted, shaped and cooled to room temperature. It is well known that colored glass articles can be made by including ingredients in the glass batch that will color the glass throughout. This method of coloring glass presents inventory problems when a plurality of colored glass articles are desired or where only portions of the article are to be colored. Low melting colored glass frits have been employed as coatings, but they are usually opaque and are unsatisfactory where colored, transparent articles are desired. Transparent metal oxide films which are developed on the glass at high temperatures have been employed, but the color selection is limited to the natural color of the oxide films. Typical patents illustrating such metal oxide films are U.S. Patents Nos. 2,584,763 and 2,593,817. Some attempts have been made to incorporate organic dyes on glass surfaces; however, problems of durability and light fastness have been encountered. For example, chrome complexes of various colorants have been applied to glass as shown in U.S. Patents Nos. 2,951,739 and 3,023,072, and British Patent No. 825,010. Colors that have the required light fastness usually have involved the use of opaque pigments or dispersed dyes. Where transparency is desired, pigments cannot be resorted to unless of colloidal dimensions.

SUMMARY OF THE INVENTION In accordance with the present invention, a coloring solution for glass mirrors has been developed which is easy to apply and which results in the formation of a transparent, durable, tightly adherent colored film on the glass surface. The colored films exhibit unusual light fastness properties. The coloring solution is composed of a stable solution of the reaction product of a hydrolyzable organic titanate and an organic dye, preferably of xanthene type.

Elihu nu sin-um- Patented July 22, 1969 The exact chemical nature of the reaction product is not known; however, it is postulated that some type of chelate structure is created by the reaction. It is further postulated that the firm bond which is created between a silicate glass and the reaction product is the result of a silicon-oxygen-titanium bonding between the silicon of the glass and the titanium of the reaction product.

The formation of the coating solution is relatively simple. It merely involves preparation of a stable solution of the titanate and addingj'the dye to the solution. This can be done at room temperature and at atmospheric pressure. It is important that a solvent or carrier be selected that will permit the'titanate to be uniformly dispersed in a stable form inthe carrier. Thus the titanate is dissolved in the solvent or suspended as a very fine, clear, colloidal dispersion in the carrier, The term solution as used herein and in the claims is intended to include and cover both of such physical forms.

The preferred solvent for the titanate is methanol; however, the titanate can be employed in any liquid carrier or solvent that resultsin a stable solution, i.e., one in which the titanate does not precipitate out as a solid. Various stabilizing agents can be employed with the titanate solution if it exhibits unstable precipitating tendencies.

One titanate ester which has been found to be particularly suitable in the practice of the invention is tetraisopropyl titanate. Other useful titanates are those described in U.S. Patents Nos. 2,614,112, 2,621,195, 2,710,267, 2,768,909 and 2,941,903. These titanates have, for example, the formula (RO) Ti wherein R is an alkyl radical having from 1 to 18 carbon atoms, preferably 1 m8 carbon atoms. The titanate solutions are described in these patents as being anhydrous, but having the possibility of the presence of a minor amount of water, such as a mixture of percentmethanol and 10 percent water. Approximately 0.1 to 20 percent by weight of the titanate is useful in the coating solution. The amount of titanate applied to the base is preferably about 0.0003 to 0.0375 gram molecule of ester per square meter of base surface. Such amount. can be conveniently obtained by use of an anhydrous solution containing about 0.05 to 0.525 gram molecule er liter of solution.

Many organic dyes canbe used in the practice of the invention. Best results have been obtained on massive glass articles such as flat glass with xanthene class dyes. These dyes are derivatives of xanthene and are characterized by the presence of the xanthylium nucleus as the chtomophore. Included in the xanthene class of dyes are the pyronines, sacchareins, succineins, rosamines, rhodamines, rhodoles and phthaleins, the latter being the preferred type. The chemical structures of xanthene and some derivatives found useful in the practice of the invention are as follows:

xanthene O HO 0 HO- %O\ 0H i I o 0 0H go o 0- fluorescein (yellow) or (gold) Br Br I 6 l HO- U03 Br Br Eosiu A (yellow-red) Br 1'31 Na0 0 Br Br COONa Eosine G (blue) I I 0 1 NaOO U0 Br- I COONa Rose Bengale luish-red) Rhodamine 6G Pyronine G (red) (red) z sh 2 5):

S O2NH3 Saccharein VI (bluish-red Rhodamlne S (p .1

OH (I)H OH 0 O HO A H2804 HO 200 C. o 0 O0 0 0H Gallein Coerulein (blue-violet) (green) The amount of dye employed in the coloring solution is difiicult to state on a weight basis due to the complex nature of the variety of suitable dye molecules. In order to get maximum effectiveness of the dye, one mole of dye per mole of titanate can be employed. Substantially lower amounts of dye on a mole basis, i.e., 0.01 to 0.5 moles of dye to one mole of titanate are suflicient to obtain good coloring. Lighter shades, of course, can be obtained by using a lesser amount of dye in relation to the titanate or by using a lower concentration of the reaction product in the solution. Furthermore, combinations of dyes can be used to get difiereut colors and hues.

It has been found that certain properties of the finished article can be improved by the addition of certain metal salts to the solutions. For example, the light fastness of the colored article is improved by the inclusion of copper salts in the solutions, especially when the final product is exposed to liquid water. Copper sulfate (hydrated or anhydrous), copper halides, such as copper chloride (CuCl copper bromide (CuBrg) and copper fluoride (CuF copper acetate and copper nitrate (Cu(NO .3H O) have been used to improve the light fastness properties of the colored articles. About 0.1 to 5 percent by weight of the copper salt based upon the weight of the coloring solution adequately serves this purpose.

The copper salts as well as some additional soluble salts serve the function of stabilizing the solution with respect to prevention of precipitation of the titanium ester from the solution. The soluble halides and nitrates of aluminum, lead, antimony and trivalent titanium aid in the stabilization of the coloring solution. About 0.2 to 15 percent by weight of these additional salts used alone or in combination based upon the Weight of the solution adequately serve this purpose. It is important to state, however, that whereas copper salts stabilize the titanium ester in the solution, they also tend to precipitate the dye in the solution in the absence of aluminum salts; therefore, both aluminum and copper are usually employed in the solution. Gelatine can be used as a substitute for aluminum in this respect.

Use of the halides of the metals described above provides the best stability or shelf life to the coloring solutions. It has been found, however, the the halide solutions produce an objectionable degree of haze and loss of silver adhesion to the glass in mirrors. This haze and adhesion accomplish the bonding of the coating to the glass. The problem does not occur in the absence of halides and curing treatment is time-temperature dependent and thus therefore it is concluded that the halide salts have some the exposure may be varied greatly depending upon the objectionable effect on the silver or the materials used in production situation. For example, exposure of the coated sensitizing the glass or catalyzing the silvering process. 5 glass article to a temperature of 1250 F. for 5 to 20 sec- The reason for this is not known and is further obscured onds is within the scope of the invention. The thickness by the fact thatf'the use of halogenated dyes, i.e., the haloof thefilms produced is 200 to 5000 angstroms, preferably genated fluoresceins (Eosin), does not create the haze 300 to 3000 angstroms. effect. Use of the nitrates and sulfates of the above-merl- DESCRIPTION OF THE PREFERRED troned metals in the coloring solutions avoids the haze in EMBODIMENTS tinted mirrors.

other materials which are useful for stabilizing the ti- Further details and e t s of he lnventlon can tanate in solution are acids such as citric and acetic acid be eXplalhed and understood In the followlhg examples:

and bases such as lithium, sodium and potassium hydroxide. Small amounts, of the order of 0.01 to 2.0 percent Example I by weight of these materials, are useful. Flat glass plates 24 x 24 x inches are dipped in The total amount of solids, i.e., titanate plus dye plus the solutions set forth in Table I. The ingredients are stabilizing agents, should not be more than 40 percent by added and mixed in a suitable glass mixing container in weight of the solution, preferably not more than perthe amounts listed and in the order listed in the table, cent by weight 'of the solution, in order to prevent pre- 2 beginning at the top of the table. No special mixing procipitation of one or more of said solids from the solution. cedure is necessary. The films are cured at 400 F. for

The solution is prepared merely by adding the ingrediminutes. The films are approximately 500 angstroms thick.

TABLE I.COMPOSITION OF VARIOUS TITANIA-DYE TINIING SOLUTIONS 1 2 3 4 5 6 7 Methanol, cubic centimeters- 00 100 AlCla-GHzO, grams; .Al(NOa)3-9H2O, grams CuSOr, grams CuSO4-5Hg0, grams. CuBrz, grams LiOH, grams 4 H2O, cubic centime Tetraisopropyl titanate, cubic centimete 10 6 6 6 Fluorescein, grams 6 2 2 Dibromotluorescein, grams 2 2 2 Eosrn,Y, rams. .IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII "Ii Color Gold Gold Gold Gold Gold Gold Flesh Flesh Flesh Red Red Red Red ents to each other and mixing them at room temperature. Some precautions are necessary during the dipping In The solution can be prepared in glass containers or in order to get a uniform coating on the flat glass. The flat plastic containers such as thise made of polyethylene, 40 glass is gripped along its top edge by a pair of tong s The polystyrene and polymethyl methacrylate. The solution glass is dipped into the coating solution in a container.

should not be mixed in containers of copper, titanium, The descent of the glass is stopped short of complete imstainless steel, aluminum, brass, galvanized steel, Inconel, mersion of the" glass so that the tongs and top edge do not Monel or lead since these metals in contact with the enter the solution. This is necessary to prevent streaking solution cause precipitation of the dye. from run-01f of the solution from the top edge of the The solution is applied to the glass article at room temglass and from the tongs upon withdrawal of the glass. perature. The application can be by dipping, painting or The glass is maintained in the solution for a length of any other method convenient for applying a uniform coattime suflicient for simple wetting of the glass surface with ing of a liquid material. the solution. Dipping for a longer period than this is not The glass mirror may be in the form of flat glass such necessary.

as made by thecommonly known plate, sheet or float proc- 5 The withdrawal of the glass from the coating solution esses. The term flat glass also includes glass articles is critical. The glass is withdrawn at a slow, steady rate,

anade according to the above described processes and therei.e., 30 inches per minute. The film formation on the glass after bent, Shaped and/01 laminated to Produce fabricated occurs as the .Ic'oated glass rises from the solution and as glass articles. Such flat glass articles are made from conth sol e t evaporates from the coating clinging to the venftional lime-soda-silica glasses. glass. Anythin'g' which changes the rate of evaporation Although it is theorized above that the bond th the during withdrawal is liable to cause streaks in the colored glass is by an Si-O-Ti linkage, it may be that the hydrolys s film on the surface of the glass which are different in ap condensatien which pp y takes place n the pearance from the remainder of the film. Such efiect may bonding of the colored film the glass Surface merely be created by the occurrence of waves on the surface of involves reaction of the film of coating solution with tightth ati b th,

ly bound hydroxyl groups normally present on e Surface The effect may also be created by turbulence or uneven of-glass articles. This would explain the success of the inmo ement of air immediately above the solution bath vention with regard to the coloring of non-silicate glasses. the b eif ting change in the evaporation rate of the This also Permits application of the invention to the solvent as the glass is withdrawn from the bath. For this Colorlhg of other materials normally having y y reason, it has been found desirable to enclose the area groups Present on their surface or Contained in the above the bath from the surrounding atmosphere in order lecular StI'IJCtUI'C Of the material. One restriction is that the to eliminate the effects of stray currents of air in the fac. material to be colored can withstand the curing p tory. Such stray currents also affect the humidity or q 'e (e moisture condition of the air above the bath, which con- After eppheatleh of the coatlhg Solution to the glass dition is an important variable which affects the evaporaf c the Coated glass article is heated to bake r e tion rate of the solvent. Likewise the temperature of the the coating on the g The heating p s n ary t air above the bath should be controlled and not allowed develop the light fa'stness properties of the the colored to vary substantially in order to insure uniform evaporafilms. Exposure of the coated glass to temperatures of tion of the solvent from the coating. These precautions 400 F. to 500 F. for 60 to 10 minutes is satisfactory to permit obtaining of films of uniform thickness which are free from iridescence. This is true with regard to films having a thickness of greater than 500 angstroms which are particularly subject to iridescence caused by thickness non-uniformity produced by conventional techniques.

During the filming of large glass plates, haze bands can develop across the plate in a direction normal to the direction of withdrawal. These haze bands are detected only after the plate is silvered for mirrors. The theory of this haze development is that the evaporation of the solvent during film forming absorbs heat from the surround ing air. Eventually the dew point of this air is reached. At this point, moisture from the air condenses on the film and this dries the air space. The lower part of the plate enjoys a normal treatment. The top part of the plate escapes this haze elfect because it is dry before the dew point is reached. It is therefore desirable to withdraw the glass at a speed which is more than suflicient to overcome this effect.

A copper coating and a protective paint backing are thereafter applied.

The mirrors are tested as described below with the results being set forth in Table II.

(1) Adhesion (pull test) .This test consists of scratching through the backing and film down to the base glass, applying Scotch tape over this area, then pulling off the tape. Poor adhesion is signified by having the backing and silver pulled from the glass with the tape.

(2) Salt spray.Mirror samples are subjected for 120 hours to a percent salt spray. An evaluation is made by noting the deterioration of the different samples.

(3) High humidity.-The samples are subjected for 60 days in a 120 F. high humidity room, then checked for deterioration.

(4) Fadometer '(Atlas Fade-Ometer).Tinted mirror samples are exposed in the fadometer, then checked for fade characteristics.

TABLE II.RESULTS OF VARIOUS TESTS OF TINTED MIRRORS Appearance Fade-Ometer (hrs) prior to test- 60 days I20 Salt spray 120 Solution Sensitizer ing Pull test F. humidity hrs. 133 331 679 926 5 SnClz Good Good Good Good No fade No fade No fade. 5 TiOls do do do .do do do Do. 12 SnGl; do ...do do Fair No fade 12 TiCla .do do do Fair-ldo l Commercially acceptable.

In the dipping process above described, the top inch or so of the plate is uncoated. This portion can be easily cut 01f after the coating is cured on the plate.

Example H.--Mirrors Tinted mirrors are made utilizing solutions Nos. 5, 8 and 12 from Table I to make respectively, gold, flesh and red tinted mirrors. Conventional plate glass samples, 4 x 5 inches, are utilized. The glass is cleaned using a 50-50 weight percent solution of water and N-propyl alcohol. The glass is then immersed vertically in the tinting solution and withdrawn smoothly at a speed of inches per minute. The film is decoated from one side of the plate using a wet cloth. The film prior to curing by heat treatment is very water soluble and easy to decoat with water.

The coated glass is heated to a temperature of 400 F. for 30 minutes, and then allowed to cool slowly to avoid breakage. The film is now durable and ready for the silvering process.

The film is sensitized by rinsing it with a solution consisting in weight percent of:

Ingredient: Weight percent Water 50 Isopropyl alcohol 49 TiCl or SnCl 1 The final steps are accomplished according to the conventional mirror process. This includes silvering by exposing the sensitized film to the following solutions:

SILVER SOLUTION The present invention has enabled the production of a plurality of colored glass articles by a novel coating method. The invention is particularly unique in that colored articles are obtained which exhibit excellent light fastness properties with organic dyes which are notoriously poor with respect to this property when previously used.

We claim:

1. A colored mirror composed of fiat glass having an opaque, highly reflective coating on a surface of theglass which has been colored by applying a thin coating of a coloring solution comprising a stable solution of the reaction mixture of a hydrolyzable organic titanate and a xanthene type dye with a solids content ofnot more than about 40% by weight of the solution and heating the coated glass for a time and at a temperature which is sufficient to develop light fastness properties to the colored glass.

2. A colored mirror as described in claim 1 wherein the solution contains a light stabilizing amount of a copper salt.

3. A colored mirror as described in claim 1 wherein the solution contains a solution stabilizing amount of an inorganic salt selected from the group consisting of the soluble salts of aluminum, lead, antimony and trivalent titanium.

4. A colored mirror as described in claim 2 wherein the solution contains a solution stabilizing amount of an inorganic salt selected from the group consisting of the soluble salts of aluminum, lead, antimony and trivalent titanium.

5. A colored mirror as described in claim 1 wherein the reflective coating is silver.

References Cited UNITED STATES PATENTS 1,604,459 10/1926 Lyons.

DAVID KLEIN, Primary Examiner US. Cl. X.R. 

